Django model cron jobs

Inspired by snippet 1126, I thought I would post a module that stores crontab entries in a database, with a less powerful, but more end-user friendly API. ("twice a week starting on Sat 1 Dec 2007, 6:23am", instead of "23 6,18 * ").

The crontab is synchronised when an entry is changed, and relevant environment variables, function name and arguments are provided. You might want to store this as an app called "scheduler" to match the imports.